The overall objective of this proposal is to develop rapid, sensitive and reproducible in situ hybridization methods suitable for the analysis of both entire chromosome domains and individual genes directly in interphase cells and to apply these techniques to the diagnosis of inherited genetic disorders and neoplastic diseases which exhibit numerical or structural chromosome abnormalities. Our specific goals are: 1) to use cloned DNA subsets that hybridize uniquely to specific human chromosomes or discrete subchromosomal regions to identify chromosomal territories in interphase cells by non-isotopic in situ hybridization. 2) to develop a simple and automated screening test to detect the major trisomic disorders (chromosomes 13, 18, 21 and X) directly in interphase cells from amniotic fluids or chorionic villi, using probes sets labeled with different reporter molecules that can be distinguished by fluorescence or colonmetric methods. 3) to detect chromosomal translocations in interphase cells that are diagnostic for specific inherited genetic diseases or neoplastic disorders using chromosome specific probe sets in combination with 3-D optical imaging techniques. 4) to improve the routine detection sensitivity of non-isotopically labeled probes in situ to the single gene level (less than or equal to 1 kb), using fluorescence and chemiluminescence detection methods that generate quantitative results, and 5) to apply the techniques developed by aim 4 to determine the intranuclear location of specific genes before and after transcriptional activation and to monitor translocations or other genetic rearrangements in interphase nucleic using defined gene probes.